Labeling diagonal arrows with the diagrams package

As far as I can tell, the following code

\usepackage[balance,small]{diagrams}

...

\begin{diagram}
&& X && \\
& \ldTo^\Phi & & \rdTo^\Psi &\\
Y &&&& Z
\end{diagram}


should produce a diagram with diagonal arrows and labels which are horizontal (i.e. not slanted with the arrows), at least that's what happens in Milne's documentation (http://www.jmilne.org/not/Mdiagrams.pdf). However my labels (Phi and Psi) are slanted along the arrow.

How do I make it so the labels are horizontal?

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If you want to, you can answer your own question (and then accept it). –  Gonzalo Medina Apr 2 '13 at 2:06
Welcome to TeX.sx! –  Kurt Apr 2 '13 at 2:12
The space above is reserved for questions and the space below is intended to be where people look for answers. It would be nice if you edited the above to be a question, and provided a self answer below. That way this could be useful to others who encounter a similar problem. –  Peter Grill Apr 2 '13 at 4:53
Ok, I wasn't sure if that was appropriate. Apparently I must wait till tomorrow to accept my answer. –  RghtHndSd Apr 2 '13 at 14:08
\usepackage[balance,small,nohug]{diagrams}